Occurrence codes and their respective dates disclose to the payer specific event(s) related to the billing period on the UB04. They are located in boxes 31 - 36 on the UB04.
To view and enter them into your patient's encounter, navigate to Billing > Live Claims Feed > Inside patient's encounter > Right side of screen > Cond & Occ tab.
The dropdown will list the specific occurrence codes that can be selected. The accompanying date can be listed in the box just to the right of the code labeled "date".